1978191077 has 8 divisors (see below), whose sum is σ = 2099683800. Its totient is φ = 1857268224.

The previous prime is 1978191071. The next prime is 1978191091. The reversal of 1978191077 is 7701918791.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 914518081 + 1063672996 = 30241^2 + 32614^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1978191077 - 2⁸ = 1978190821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978191071) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 135302 + ... + 149207.

It is an arithmetic number, because the mean of its divisors is an integer number (262460475).

Almost surely, 2^1978191077 is an apocalyptic number.

1978191077 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

1978191077 is a deficient number, since it is larger than the sum of its proper divisors (121492723).

1978191077 is a wasteful number, since it uses less digits than its factorization.

1978191077 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284935.

The product of its (nonzero) digits is 222264, while the sum is 50.

The square root of 1978191077 is about 44476.8600173169. The cubic root of 1978191077 is about 1255.3247154772.

The spelling of 1978191077 in words is "one billion, nine hundred seventy-eight million, one hundred ninety-one thousand, seventy-seven".